1. Field of the Invention
The present invention relates to a magnetic disk drive for recording information on, and reproducing information from, a magnetic disk and, more particularly, to a loading mechanism for moving a disk cartridge between an unloading position and a loading position.
2. Description of the Related Art
This type of magnetic disk drive uses a disk cartridge housing a magnetic disk in a casing. The disk cartridge is inserted into the magnetic disk drive and the magnetic disk is driven to store and reproduce information.
FIG. 13 is for explaining the disk cartridge to be used in this type of magnetic disk drive, in which a disk cartridge 70 houses a magnetic disk 71 in a synthetic resin casing 72.
A corner of one end of this casing 72 is cut off in a tapered shape to form an insertion error preventing portion 73. The opening 74 is formed in one end side of the casing 72, and a shutter 75 made of a thin metal plate is slidably attached along the one end edge of the casing 72.
The shutter 75 is provided with a window 76 formed correspondingly to the opening 74. The shutter 75 is being constantly pressed in the direction of the arrow g by an unillustrated spring which is built in the casing 72, closing the opening 74. When the shutter 75 slides in the opposite direction of the arrow g against the spring force, the window 76 comes into alignment with the opening 74; that is, the shutter 75 is opened, exposing out the magnetic disk 71 housed in the casing 72.
Next, FIG. 10 to FIG. 12 are for explaining the prior art magnetic disk drive. The disk drive is mainly comprised of a cartridge holder 80 for holding a disk cartridge loaded; a slide plate 81 which moves the cartridge holder 80 between the unloading position in which the disk cartridge is loaded and unloaded, and the loading position in which information is stored in, and reproduced from, the magnetic disk 71; a chassis 82 slidably supporting the slide plate 81; a carriage 84 mounted with a lower magnetic head 83b and movable in a diametral direction of the magnetic disk 71; a hold case 85 vertically movably supported in the carriage 84 and mounted with an upper magnetic head 83a; and an unillustrated spindle motor for driving to rotate the magnetic disk 71.
The slide plate 81 is made of a thin iron plate, and its both right and left ends are bent into a U shape to thereby form a pair of side walls. As shown in FIG. 10, another end of a coil spring 86 retained at its one end on the front side of the chassis 82 is retained, so that slide plate 81 is pressed towards the front side (in the direction of the arrow b) of the chassis 82, thereby being locked in this state by a lock mechanism not shown. The pair of side walls of the slide plate 81 are provided with inclined cam grooves 81a correspondingly to four projections 80a formed on both sides of the cartridge holder 80. These projections 80a are positioned above the inclined cam grooves 81a as shown in FIG. 11, to thereby support the cartridge holder 80 in the unloading position previously stated.
On the back side of the chassis 82 the carriage 84 is mounted. As shown in FIG. 11, a pair of arms 85a formed on the hold case 85 are in contact with the upper surface of the cartridge holder 80. In this state the upper magnetic head 83a is off the lower magnetic head 83b.
In this state, the disk cartridge 70, when inserted into the magnetic disk drive, is received by the cartridge holder 80, which, with the shutter 75 opened, holds the disk cartridge 70 and is released from the above-described unillustrated lock mechanism. Then the slide plate 81 slides in the direction of the arrow g by the force of the coil spring 86. With the sliding of the slide plate 81, the projection 80a moves downwardly from the upper part of the inclined cam groove 81a to the lower part of the inclined cam groove 81a as shown in FIG. 12, allowing the cartridge holder 80 to move downwardly from the unloading position to the loading position. With this movement, the magnetic disk 71 is set to the unillustrated spindle motor mentioned above and at the same time the hold case 85 tilts down to lower the upper magnetic head 83a into contact with the magnetic disk 71. That is, the magnetic disk 71 is held between the upper and lower magnetic heads 83a and 83b, being rotated to record information in, or reproduce information from, the magnetic disk 71.
To take the disk cartridge 70 out of the magnetic disk drive after the recording/reproducing of information, the slide plate 81 is slid towards the back side of the chassis 82 (in the opposite direction of the arrow b) against the force of the coil spring 86; then the projection 80a is moved upwardly from the lower part of the inclined cam groove 81a and the slide plate 81 is locked by the unillustrated lock mechanism previously stated, thus allowing the cartridge holder 80 back to the original unloading position.
With the movement of the cartridge holder 80 from the unloading position to the loading position, the upper magnetic head 83a is lowered by the force of the coil spring 86. In this case, however, the upper magnetic head 83a, if moving down abruptly, will give damage to the magnetic disk 71. It is, therefore, necessary to control the speed of downward movement of the upper magnetic head 83a.
In the magnetic disk drive, as shown in FIG. 10, a rotary oil damper 87 mounted on the chassis 82 is engaged with the slide plate 81. When the slide plate 81 slides in the direction of the arrow b with the force of the coil spring 86, a resistance force is produced by the rotary oil damper 87 against the force of the coil spring 86, reducing the speed of sliding of the slide plate 81 and consequently slowly moving the upper magnetic head 83a downwardly into gradual contact with the magnetic disk 71.
The prior art magnetic disk drive described above, however, has such a shortcoming that since the rotary oil damper 87 which reduces the speed of sliding of the slide plate 81 is expensive, the cost of the device can not be decreased.